1. Field of the Invention
The present invention relates to an oscillator for the microwave band or the millimeter wave band provided with an oscillation circuit using, for example, a Gunn diode and provided with an output transmission line to output an oscillation signal. The present invention also relates to radio equipment using the oscillator.
2. Description of the Related Art
Up to now, in oscillators for the microwave band and the millimeter wave band using a negative-resistance element such as a Gunn diode, etc., an injection-locking type oscillator has been used, as disclosed in-Japanese Unexamined Patent Application Publication No. 10-145143.
When such an oscillation circuit which performs multiplying oscillation is used, an oscillator for the millimeter wave band above, for example, the 60 GHz band, which cannot be directly oscillated by Gunn diodes, etc., can be constructed.
However, in the conventional oscillator disclosed in the above-mentioned publication, bandpass filters (BPFS) and high-pass filters (HPFS) are required in the output circuit to suppress the fundamental wave, and the circuit construction becomes complicated. Furthermore, because of such a circuit for suppressing the fundamental wave, there also arises the problem of increased loss of components of the frequency to be output.
Accordingly, it is an object of the present invention to provide an oscillator which solves the above-mentioned problems, which is appropriate for mass-production and cost reduction, and which also reduces the number of parts due to a simple construction, and to provide radio equipment using the oscillator.
Furthermore, it is another object of the present invention to provide an oscillator in which the fundamental wave is fully suppressed and which exhibits low loss, and to provide radio equipment using the oscillator.
In an oscillator of the present invention which comprises an oscillator circuit constructed on a dielectric substrate and an output transmission line for transmitting an oscillation output signal of the oscillation circuit, the output transmission line comprises a transmission line in which a portion of dielectric material is contained between two substantially parallel conductor surfaces and which has cutoff characteristics, a cutoff frequency of the transmission line being determined so that one of a fundamental wave component and a combination of the fundamental wave component and lower-order harmonic components are cut off and a higher-order harmonic which is higher than the components is propagated. The oscillation circuit is constructed by mounting a negative-resistance element in a line, and injecting means for injecting a signal of the frequency of the fundamental wave into a bias line for supplying a bias voltage to the negative resistance element is provided.
In an oscillator of the present invention the output transmission line comprises a dielectric line in which a dielectric stripline is disposed between the two substantially parallel conductor plates.
In an oscillator of the present invention, the negative-resistance element is connected to a line made of a conductor pattern formed on a dielectric substrate, the output transmission line is coupled to the line, and, when the wavelength on the line is denoted by xcexg, the length from the connecting location of the negative-resistance element to an the closest end portion is xcexg/4+N1xc3x97xcexg/2 where N1 is an integer over zero, and the length from the connecting location of the negative-resistance element to the coupling location of the output transmission line is xcexg/4+N2xc3x97xcexg/2 where N2 is an integer over zero.
In an oscillator of the present invention, the output line is a dielectric line in which a dielectric stripline is disposed between the substantially parallel conductor plates, and by forming a slot in one conductor plate and by disposing the dielectric substrate outside the conductor plate, the line of the oscillation circuit and the dielectric line are coupled.
In an oscillator of the present invention, the dielectric substrate is housed inside a case, a wide portion and a narrow portion are provided in the bias line, and in the vicinity of a narrow portion a spring for fixing the dielectric plate to the inside surface of the case is provided.
Radio equipment of the present invention is constructed by using any one of the above oscillators.